title: Depth of cure of light-cured composite resin with light-curing units of different intensity.
abstract: An increase in light intensity is known to produce greater surface hardness of composite resin. The purpose of this study was to determine the depth of cure produced by two light-curing units with different light intensity outputs. Two light-curing units were selected, the one producing 600 mW/cm2 and the other 300 mW/cm2. Five metal plates with thicknesses 1, 2, 3, 4 and 6 mm were selected and 20 holes of 5 mm diameter were drilled through each plate. Each hole was slightly over filled with composite resin (Z100, 3M), covered with a polyester strip, compressed, and light-cured; 10 samples on each plate with the 300 mW/cm2 unit and 10 samples with the 600 mW/cm2 unit. The bases of all samples were subjected to Vickers Hardness testing immediately and one hour after curing. Results were analysed with the Student-t-test. There was a decrease in Vickers Hardness with every increase in depth. Significant differences were found between all the immediate and one hour groups, between the 300 and 600 mW/cm2 light intensities at 2 mm depth and the 2 mm and 3 mm groups. Increments of light-curing composite resin should not exceed 2 mm; optimal hardness only developed after one hour; at a depth of 2 mm an increase in light intensity produced a significant increase in Vickers Hardness; beyond 2 mm depth the increased light intensity did not produce a significant increase in Vickers Hardness.
authors.affiliation: Department of Restorative Dentistry, Faculty of Dentistry, University of Pretoria.
authors.forename: J T
authors.initials: JT
authors.lastname: Marais
authors.forename: M F
authors.initials: MF
authors.lastname: Dannheimer
authors.forename: P J
authors.initials: PJ
authors.lastname: Germishuys
authors.forename: J W
authors.initials: JW
authors.lastname: Borman
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D006244:Hardness; D006245:Hardness Tests / Q000379:methods; D008027:Light
chemical_list: D003188:Composite Resins